Currently, louver films in display applications only deliver acceptable performance when viewed by a viewer along a louver axis. Currently, louver films have a uniform louver angle, louver pitch, and film thickness across the louver film. A viewer's angle of view, however, changes across the display (e.g., the angle of view at the center of the display is different than at edges of the display). This change in the viewer's angle of view across the display causes two problems: 1) luminance is reduced when a viewer looks at the edges of the display; and 2) light is emitted at angles outside of and not visible to the viewer's field of view, which may cause unwanted reflections off nearby reflective surfaces (such as a bubble canopy of an aircraft cockpit, a window of a vehicle, a window of room, another display, or the like).
Micro-louver films have been used to restrict the angle at which a display may be viewed. Micro-louver films restrict the transmission of light through the use of tightly spaced, embedded louvers (which are typically black). Micro-louver films are typically constructed using small, absorptive louvers to restrict the angular profile of transmitted light through the film. Currently, these parameters are fixed in one axis across the entire film. Micro-louver films are typically used in applications requiring privacy and security, such as to prevent unauthorized viewing of private information on a monitor or public-use kiosk (e.g., an automatic teller machine (ATM), etc.). Given the high non-recurring cost to manufacturer custom micro-louver films, they are offered in a limited selection of louver pitches, louver angles, and film thicknesses for a limited selection of viewing angles. Such manufacturing limitations diminish the ability to tailor a luminance profile across a display for specific applications (e.g., military cockpits, etc.).
Previous attempts to direct the light towards the viewer while reducing stray light emissions have included the use of light shaping diffusers and optical films (e.g., micro-prismatic brightness enhancement and light turning films, etc.). While such light shaping diffusers and optical films typically provide more transmission and are helpful in steering more light towards the user, they do not provide the same level of off-axis light suppression as compared to micro-louver films. In addition, light shaping diffusers and optical films are rendered ineffective when placed behind micro-louver films due to louver off-axis light absorption properties. Additionally, neither light shaping diffusers nor optical films provide a solution to account for the change in angle of view when looking across the display surface.